In the processing of recovered paper in the recycling process, residual matter remains after the elutriation of the mechanical desludging. This residual substances can contain, in varying amounts, concentration and type, clumped paper, cardboard remnants, plastic pieces, wood residues, metal parts, and more besides. As a whole, these residual substances are called rejects. After exiting the elutriation process and, if necessary, after intermediate deposition during which a gravimetric dewatering can occur, these rejects are, in general, deposited at a hazardous waste landfill.
At this point, these rejects contain an average of 50% water, which can occur as surface water and also as water absorbed in the paper and wood portion.
Various methods and devices are already known or have been described which include the utilization and, in particular, the thermal treatment of waste, residual substances and rejects.
A method for the thermal recovery of non-recoverable waste products is known from DE 41 39 512 A1. In this case, the non-recoverable waste products are household refuse, industrial waste containing plastics, paint residue, scrap tires, shredder light material from the recycling of scrap cars, or waste contaminated with oils. According to this method, these non-recoverable waste products are subjected without costly pretreatments to a combination of known processing stages, such as pyrolysis, crushing, classification, gasification and gas cleaning. This method is intended on the one hand to produce a clean gas suitable for versatile material and energy uses, and on the other to yield elutriation-proof, useable or easy to dump purely mineral, solid residue, while at the same time ruling out toxic impact on the environment.
Furthermore, according to DE 44 41 423 a method and device are known that are used to extract useable gas from waste by means of pyrolysis. With this method, the crushed waste is loaded in a pyrolysis drum sealed gas-tight, in which the pyrolysis gas is produced and the pyrolysis residue is separated. The pyrolysis gas is split into a cracked gas in a gas transformer with the addition of air and in the presence of a red-hot coke bed. The heat necessary for pyrolysis is transferred by a gas in direct contact with the material to be pyrolyzed. A partial stream of this gas is the cracked gas leaving the gas transformer.
A method for utilizing a starting material is also known from DE 43 34 544. With this method the starting material of polymer or other packing material with or without residual content that can be carbonized or not or pyrolyzed or not, is loaded in a reaction chamber. In this reaction chamber the components that can be carbonized are carbonized and the components that can be pyrolyzed are pyrolyzed, the gases produced being used as energy sources for a firing and the residual substances being taken out for further treatment.
According to DE 42 09 549 a method is known for the thermal treatment of residual substances, e.g. for the separation and recovery of metal compounds with organic content by means of a combination of pyrolysis and gasification. According to this method, the residual substances are separated in a gas and a solid phase and decomposed by means of pyrolysis at 300 to 700° C. Existing, usable products are separated from the solid phase and the remaining materials, together with the gas phase, are gasified to fuel gas with oxygen-enriched air or oxygen at temperatures>1300° C.
Furthermore, a method is known from DE 36 32 105 for removing fissile contaminants from a pyrolysis gas. Accordingly, the pyrolysis gas, which was produced by the pyrolysis of a material containing carbon and/or hydrocarbon, is fed into a reaction chamber together with a gas heated in a plasma generator, and there the contaminants are split off so that the gas can now be supplied directly to the consumer.
According to DE 38 26 520 A1, a method is also known for the pyrolysis of sewage sludge in an externally heated, fixed reactor with an internally located transport apparatus, in which the pyrolysis, as a controllable process separate in terms of time and location, is carried out in several stages of drying, heating to decomposition temperature, pyrolysis in several temperature ranges and recovery of the pyrolysis residue as fuel.
The first stage here is dewatering the sewage sludge, the second stage is heating the dried product to 200–250° C., the third stage is the thermal decomposition of the sewage sludge to pyrolysis gases and a carbonaceous residue at 251 to 700° C., preferably at 300–500° C., and the fourth stage is the combustion of the pyrolysis gases produced and the application of the hot gas to heat the reactor in separate heating zones according to stages 1, 2 and 3.
Furthermore, a method and a device are known from DE 34 17 620 that are used to produce thermal energy that can be converted into mechanical energy from the incineration of wet waste. The invention assumes that the moisture in wet waste must be removed before it can be incinerated. A heat source for drying the waste here can be the steam that vaporizes from the wet waste, or the other heat source is the flue gas from the incineration plant. The device for implementing this invention comprises a waste drying apparatus with a feed screw, a continually agitating dryer, a second feed screw, a closed and insulated conveyor, an air supply chamber, an air supply plant with a blower and three air preheaters and a thermal energy supply plant for the dryer with a pressurizing apparatus and a supply unit.
A device for treating materials containing aluminum is furthermore known from DE 42 37 161 A1. This device comprises an indirectly heated rotary kiln with a conveyor arranged inside a gas-tight revolving cylinder, two sluices and a feed hopper and a wire shaking apparatus. The conveyor inside the gas-tight revolving cylinder is a conveyor screw that is used to circulate the product treated.
Furthermore, a plant is known from DE 195 28 018 A1 for the thermal treatment of materials with organic components, in which a revolving cylinder is arranged essentially concentrically around a shaft and connected to it, inside a housing that can be filled with hot gas.
According to DE 43 37 421 A1 a multistage, high-temperature incineration of waste products with inert components and a device for carrying out this process are known. In a first stage at first an hypostoichiometric incineration and in the second stage a further incineration is carried out in a closed chamber.
Maintaining high safety standards is disadvantageous with all of these methods and devices, since the processing stages applied, in particular pyrolysis and gasification, have to be carried out in part with the exclusion of air and at high temperatures.